Pile fabric



3 Sheefts-Sheet 1 Oct; 27, 1953 w. E. COWIE ET AL FILE FABRIC Filed May25, 1950 Jill/Enrol? MLBUP. L. COME ARTHUR E .B! all/w Arrris.

W. E. COWIE ET AL Oct. 27, 1953 PILE FABRIC .5 Sheets-Sheet 2 Filed May25, 1950 Jumswrok ML 81/)? f. COW/E.

14977101? .BL0u//v. BYWW A 7'TY8- Oct. 27, 1953 w. E. cowuz ET AL2,656,586

FILE FABRIC Filed May 25, 1950 3 Sheets-Sheet 5 F gs: .bvvavrol? Arr 5.

Patented Oct. 27, 1953 UNITED STATES PATENT OFFICE PILE FABRICApplication May 25, 1950, Serial No. 164,086 In Canada May 28, 1949 12Claims. 1

This invention is for improvements in or relat ing to pile fabrics forcold Weather clothing, par ticularly for wear under the climaticconditions of the polarregions.

evaluated the several other factors bearing upon the construction of apile fabric which is to be capable of affording adequate protection tothe wearer under polar climatic conditions.

An object of the invention is to provide an im- 5 As a result of ourinvestigations a variety of proved light weight pile fabric which iscapable pile fabrics have been constructed which have of readilyshedding frost substantially without been fashioned into body clothingand tested undetriment to the fabric andv which has thermal der severeoperational conditions in the Arctic. insulation, vapour permeabilityand other char- The novel pile fabrics and body clothing soproacteristics appropriate to its employment as a fur 19 duced areconsidered to constitute a notable imsubstitute in body clothing forwear under the provement over fabrics and. fabric clothing hithsevereclimatic conditions of the polar regions. erto available for coldweather protection and A further object of the invention is to provideeven to surpass in performanc the caribou fur such a fabric which canreadily be mass-produced clothing of admitted excellence evolved by theby conventional weaving processes. 1 Eskimos through centuries ofexperience with the For long term wear under polar climatic condi Arcticclimates. tions, body clothing must either prevent the ac- The severalcharacteristics of our improved fabcumulation of frost within theinsulating layers rics, which characteristics are to a certain extent orthe clothing fabric must be so designed that inter-related, will bediscussed under separate such accumulations may periodically be removed.20 eadings as follows:

Th accumulation of frost within the insu1ating layers may of course beprevented by enclos- FROST REMOVAL ing them within a water impermeableenvelope We are satisfied that the superiority of Wolverbut this has notso far proved to be practical. ine hair can adequately be accounted forsolely In regard to the periodic removal of frost it has on the basis ofits mechanical properties. Furs long been known to employ a fur ruffaround the not yet studied may possess similar mechanical the edge of aparka to protect the face of the properties but, of those tested,Wolverine guard wearer under polar climatic conditions and perihairfibre is unique in exhibiting all the following odically to remove fromthe ruff frost formed by qualities: condensation of moisture exhaled inthe breath and a consistent preference has been shown for 53 g i gg' 1tWolverine fur as an edge trimming. This pref- (C) A smooth 0 9 pe erencehas been ascribed to various factors but r and a 1 (d) The greatestfilament dlameter within the ppears 1n genera, to be based upon thesuperior Carnivora order with 1 frost-shedding or de-icing properties ofWolverine of 185 Su coniequen t P F fur. Thus, whil Wolverine furcollects frost or s r ace we per g1 Jen Welght of ice in the same way asany other fur, when the The average measured characteristics of the fr hs changed to i i y be removed y uard hairs of certain of the differentfurs inknocking and brushing without detriment to the vestigated areshown in Table I as follows;

TABLE I Constant Wolverine Muskrat ggg Caribou High Low titties-.1:0.06323 0. 062 0. 1162 Wolvermhm 5 Weight per inch in 0.00017 0.0000630. 00013 D Density ins c. 0. 93 0. 01 0.088 130' N0. of guard hairs perin 1888 2740 Tension in lbs. on Scott Tcster.... 0 18/1%" 0.05/0.65,135;

fur, whereas most other furs are permanently harmed by this treatment.

We have investigated the chemical and physical characteristics ofWolverine hair and of the hair of a number of other fur-bearing animals,to ascertain why Wolverine fur is superior to others A standard Scotttester (used for measuring the termining the tensile strength of thevarious hair fibres and our results show that it take a pull of 0.18 lb.(81.7 gms.) to break a single 1%" long Wolverine hair Weighing 0.00017gm./inch, which in shedding frost and we have surveyed and 55corresponds approximately to a filament of 60.25

denier. The tensile strength of Wolverine hair is eiore shown to beapproximately 1.36 gms. per

THE FILE FILAMENTS Our experiments have pointed to the; desirability ofa pile fabric having monofilaments firmly anchored to the ground cloth,to withstand the stress of combing and brushing to remove matted frost,and to the employment of pile filaments selected with regard to thefol-lbwin'g spe cial characteristics:

(2) They shouldbe straight, shouldhave a smooth surface and should besubstantially uniformly distributed over the fabric surface,

(it) They should have a tensile strength of not materially" less thanthat of Wolverine f-ur guard hair.

(i-ii) They should retain their flexibility and strength at polarsub-zero temperatures and preferably down to temperatures at least aslow as 60 F.

(iv) They should have a low-moistureabsorption capacity at high relativehumidities (i. e. less than that of cotton fibre),

(12) They should have a stiffness sufficient to maintain themselves in asubstantially sepa-' rate condition to resist compression and felting ofthe pile so to allow it to be combed or beaten to remove accumulatedfrost.

The pile filaments to be employed in accordance with the inventionpreferably consist of extruded non-cellulosic thermoplastic filamentspreferably s'elected from the group comprising the polymeric amides(known generically as nylon),

or the vinyl resins comprising, for example, the copolymers of vinylchloride and vinyl acetate (known for examplaunder the registeredtrademark Vinyon) or the vinylidene chloride polymers (known, forexample, as Saran). natively, polyacrylonitrile fibres (known under thetrade-mark Or1on-) have characteristics suitable for use in accordancewith the invention.

Of the foregoing materials, .high tensile nylon filaments have provedeminently satisfactory in in practice and fully satisfy the prescribedspecial characteristics in being straight, in having a smoothsubstantially cylindrical surface, in having an average moisture regainof 6.30% at relative humidities as high as 90%, (approximately PILEFILAMENT DENIER As previously stated, the pile filaments should Alter- 4have a tensile strength not materially less than that of Wolverine furguard hair and a stiffness sufficient to maintain themselves in asubstantially separate condition to resist compression and felting. Wehave determined that a lol-denier monofilament with characteristicssimilar to that of. nylon is about the lowest denier pile filament whichis suitablefor use in our improved fabric. Theioptimum denier is thestiifest monofilament which can be worn in comfort towards the skin; weestimate this to be at to denier when no underclothingi is worn to aboutor possibly denier with underclothing.

THE FILE STRUCTURE In addition to the foregoing requirements, a pilefabric for body clothing under polar conditions must be light in weight,flexible and have a low bulk and must possess thermal insulation andvapour permeability characteristics appropriate to the climaticconditions concerned. Thethermal insulation. of the; fabric: isdetermined.

inter alia, by the thickness and state of immm bility' of. the air layertrapped within the pile and, therefore, varies with the length of the.pile. Moreover, if the fabric is subject to conditions of use tending toflatten the pile, the thermal insulation depends also upon the abilityof the pile to resist compression and to return: to its originalcondition when the compression load is removed. The ability of a pilefabric to retain its thickness under intermittent compression loading isthus a function of the stiffness and resilience of the pile filamentsand also of the overall bulk density of the pile, which varies as thenumber of the pile threads. The nature of the ground cloth employed, thedenier of the pile thread, the resistance of the pile thread to weavingstresses and the technical limitations of pile weaving machinery, areall factors which. operate to set a practical upper limitto the count ofthe pile filaments. The overall bulk density of the pile is also largelyinfluenced by the. overall weight of the fabric. In the course of ourexperiments it has been determined by trial in the Arctic that clothingwhich weighs more than 12 to 14 lbs'., including handgear and fcctgear,tires the wearer rapidly in proportion to theincrease in weight. Themaximum practicable weight of body clothing for the conditions envisagedis of the order of 10 to 12 lbs. It is, therefore, of criticalimportance that the bulk density of the fabric be held to a minimum,which calls for the employment of a ground cloth which is as light aspossible and for a pile having a minimal bulk density consistent withthe required insulation.

In setting the physical limits of the pile struc tures which will yieldfabrics sufiiciently warm for body clothing under polar conditions, wehave studied the structure of various furs and we have selected caribouas a standard of excellence, proved by centuries of use by the Eskimo tobe the most suitable for body clothing in the Arctic winter, to beattained or surpassed. The features which render caribou skin sodesirable are its low bulk, stiffness and weight combined with adequatewarmth and its ability to withstand the conditions of service overperiods of months while on the trail. Thus, Stefansson states in hisArctic Manual (1945) that As protection against the weather of thevarious seasons, the Eskimos have developed on the whole better garmentsthan probably any people in history and further, caribou is the best ofall native Arctic materials for winter clothes For use in pile fabricsrequired for insulating purposes large diameter, low density, tightlypacked filaments are desirable such as occur naturally in caribou furwhich has 6660 guard hairs per square inch with a diameter of 0.024 cm.and a density of 0.080. Wolverine guard hair on the other hand, has adiameter of 0.0096 cm. and, therefore, to maintain the same proportionof diameter to number of hairs as caribou, should have 16,700 guardhairs per square inch. However, the can trolling factor is the overallbulk density, as that is a measure of the weight of the material for agiven amount of insulation, and the specific gravity of caribou guardhair is only a fraction of that of Wolverine and of artificial filamentspossessing the required tensile strength so that it is necessary to usea proportionately lower denier of synthetic filament to obtain theoptimum bulk density of the pile fabric. With these considerations inmind we have experimented with a number of pile fabrics utilizingartificial h fabrics possessing appropriate thermal insulation, lightweight, flexibility and low bulk density can be obtained by employing anumber of pile filament ends per unit area of fabric which is of thesame order as that of the guard hair in caribou fur. Good thermalinsulation can, however, be obtained notwithstanding that the numher ofpile filaments per unit area of fabric varies between wide limits,provided that a corresponding adjustment is made in the denier of thefilaments. The practical limits of filament count have been found tocoincide approximately with the range 2500 to 18,500 filament ends persquare inch of pile area.

To assist in arriving at appropriate packing densities using filamentsof different denier we have formulated an approximate rule relating thenumber of filament ends per square inch of pile area and the denier offilaments concerned; the rule provides that the number, N, of filamentends per square inch of pile area should be of gravity approximating tothat of dry nylon fibres In the present spe (i. e. of the order of1.14). cification the expression number of filament ends per square inchconnotes the total number of individual pile filaments which stand outfrom the ground cloth. Thus, supposing a pile warp thread is usedconsisting of 220 denier 16 filament thread used singly, each tuft thenconsists of a bundle of 16 filaments anchored in the ground clothintermediate their ends. There will thus be a total of 32 filament endsstanding out from the ground cloth for each tuft. Assuming the number ofseparate tufts per square inch to be 482, the total number of filamentends per square inch is given by 32 482:l5,422.

PILE LENGTH The weight per unit area of the fabric is, of course,approximately proportional to the pile length (other factors remainingconstant) and it is essential in using the fabric for body clothing forthe climatic conditions in question, to keep the pile length at aminimum consistent with securing the required thermal insulation. Wehave established that a relatively short pile is adequate to immobilizethe air within the pile to provide the required thermal insulation.

While there is no sharply defined lower limit for pile length, ourexperiments indicate that the minimum pile length for inner garments forArctic wear is of the order of inch. The thermal insulation of theclothing is almost directly proportional to the pile thickness and wehave determined by test that an Eskimo type construc tion must consistof two 4 inch pile layers to be effective in the Arctic winter climate.For inner layers in moderately cold climates the practical lower limitof pile length is considered to be ,4; inch. The foregoing pilethicknesses are also such as to allow the clothing to follow the contours of the body more closely by compressing the pile to some degree onthe inside garment over protruding irregularities of the body. It is ofadvantage to use thicker piles (for example up to about inch) forextreme cold, in which case the pile filaments should be selected at alarger diameter and of the filament range to maintain adequatecompression resistance and to keep the pile in an erect unmattedcondition. Under the latter conditions it is also advantageous to usehollow or cellular pile filaments to assist in keeping the weight of theclothing below the limit of tolerance, i. e. lbs.

AIR AND VAPOUR PERMEABILITY The air and water vapour permeability of theground cloth of the fabric is of critical importance for body clothingunder polar climatic conditons. The lower limit of air permeability ofthe fabric is, of course, zero and is preferable if it can be attainedwithout unduly decreasing the water vapour permeability. When the fabricis to be used for clothing in areas subject to high velocity winds ofthe order of more than miles per hour at sub-zero temperatures, it is ofprime importance that the air permeability be not greater on the averagethan about 5 cubic feet per square foot of fabric per minute, asmeasured at a pressure difierential of ,4; inch of water in the Schieferand Boyland apparatus described in Research Paper R. P. 1471 of theJournal of Research of the United States Department of Commerce,National Bureau of Standards, vol. 28, May 1942. At lower velocity windsthe air permeability may be somewhat higher but should be maintained ata value not in excess of 10 cubic feet/square foot/minute, measured asabove, for use in wind velocities from 25 miles per hour down to 10miles per hour. The air permeability of caribou clothing skin measuredby the above method ranges from about 0.5 to about 6.0 cu. ft./sq.ft./minute.

The water vapour permeability should on the other hand he as high aspossible consistent with a low air permeability and should preferably benot less than a dry tanned deer or caribou skin as set forthhereinafter. There is no sharp demarcation of desirable vapourpermeability but vapour impermeable materials produce an undesirableaccumulation of moisture within the clothing. As a minimum requirement,the pile fabric should have a water vapour transmission per square metreper single layer per hour of 20 grams for a vapour pressure differenceof 10 mm. of mercury, of 50 gms. for a vapour pressure difierence of mm.of mercury and of 80 gms. for a vapour pressure difference of mm. ofmercury, measured at body temperature on one side and 0 C. on the otherside.

The desired limits of air and vapour permeability may be achieved whilesimultaneously securing good anchorage of the filaments to the groundcloth and without adding substantially to the overall weightof thefabric by a controlled application of a cementing or bonding agent ofsuitable viscosity to the ground cloth. As. bonding agent, we may employpre-vulcanised or vulcanisable natural, synthetic or reclaimed rubber,coated from aqueous emulsion or from solution onto the back of the wovenfabric, so. as lightly to impregnate the back and to form a thincontinuous liquid film over the backing.

The rubber boding agent must have a high viscosity, of the order of 1500centipoises, so that it does not penetrate the backing and run into thepile. The coated rubber isv then dried, or cured and dried, and theamount of rubber applied is so controlled that the drying processruptures and thin liquid film over the larger pores in the backingthereby providing passages for vapour transmission. The weave of theground fabric ensures that, sufficient pores are available for therequired vapour transmission and that the pore size .is small enough tokeep the air permeability down to the required limits. The rubber also.looks the pile filaments firmly to the backing and the light penetrationof the rubber into the ground cloth reduces the water absorbency of theground cloth. An amount of rubber not exceeding 1 ounce (avoirdupois)per square yard of fabric has been found to provide excellent filamentanchorage and to give air and vapour permeability within the requiredlimits.

Thermoplastic bonding agents may alternatively be employed in emulsionor in solution.

required low air permeability of the backing may also be achievedwithout impregnation by a fluid bonding agent either by the closeness ofthe weave of the ground cloth or by using thermoplastic fibres in thebacking yarns and by passing the fabric back-down over heated rolls toflatten out the filaments and to seal up the back of the fabric.

While our experiments have shown that pile fabrics having an airpermeability not greater than 5 cubic feet per minute are suitable forbody clothing under the most severe conditions of a polar winter, itshould be understood that pile fabrics which are substantiallyimpermeable to air are also within the scope of the invention providedthat the required vapour permeability limits are conserved. The overallweight of such substantially air-impermeable structures is, however, ingeneral greater than that of the equivalent air-permeable structureswhich latter constructions are accordingly preferred on the basis ofweight.

PILE WEAVE The pile thread may be woven into the ground cloth by thewell-known cut pile weaving technique and the so-called W-weave ispreferred as enhancing the anchorage of the pile filaments.

THEGROUND CLOTH The weave of the ground cloth is susceptible to widevariation but should be selected having regard to the following specialcharacteristics:

(a) High flexibility with. a low weight,

(1)) High tensile strength per thread to withstand weaving stresses,

(c) I-Iigh tensile strength per unit cross section to withstand wearingstresses, and

(d) A low moisture absorbency.

A cotton-warp and a cotton-filled ground cloth has given good results, anylon-warp and a cotton-filledground cloth has also proved satisfactoryand, an all-nylon ground cloth has also been employed and, of the. threestructures, is preferred owing to the lower inherent moisture absorbencyof nylon.

CLOTHING CONSTRUCTION The flexibility of the pile fabric when made intobody clothing should be high to provide ease of movement and to conservethe energy of the wearer for work tasks. The drape of the fabric is alsoimportant in ensuring that when made. into clothing it does not hang toofar from the body and leave voids beneath. Such voids chill the wearerdue to convection currents and to excessive ventilation due to flappingof the clothing when the wearer moves. The wearer should also havelittle consciousness of the bulk of the clothing and in this respect theresistance to compression under the armpits and around the joints isimportant. To achieve perfection the clothing should simulate thefluidity of air.

We have established that maximum flexibility, the required drape,minimal consciousness of bulk and minimal resistance to compression canbe achieved by the Eskimo style of garment comprising two layers of pilefabric in a back-toback construction. With this arrangement, theresistance to motion across the face of the pile is very slight as smallforces at right angles to the pile filaments easily deflect the pile andallow movement of the contacting body relative thereto. The ends of thepile filaments move in the direction of the deflecting force and whenflattened present the smooth rounded surface of the sides of thefilaments to the contacting object. Such material has very littletendency to snag on surrounding objects and allows the wearer to reach,or enter bodily into areas difficult of access to the wearer ofconventional flat woven fabric clothing.

In order that the invention may be more fully understood, severalexamples of pile fabric constructed accordance with the invention willnow be described, the construction being illus trated in Figures 1, 2and 3 which:

Figure l is a diagrammatic plan View of the face of the pile fabricgreatly enlarged to show the fabric and pile structure.

Figure 2 is a cross-sectional elevation of the fabric weftways on theline 2-2 of Figure 1 and Figure 3 is a cross-sectional elevation of thefabric warpways on the line 3-3 of Figure l.

A specific embodiment of body clothing intended for wear in the polarregions and consisting of pile fabric pursuant to the invention willalso be described with reference to Figures 4 and 5 in which:

Figure 4 shows the inner garments of a parka and trousers assembly, and

Figure 5 shows the assembly completed by the addition of an outer parkaand outer trousers.

The pile fabric shown diagrammatically in Figures 1 to 3 consists of aground cloth made up of warp yarns l l and weft picks or filling yarnsi2, and a pile comprising a plurality of individual tufts i3 of pilewarp yarns beaten up in a tight w-weave with the weft yarns. The tuftsit are distributed uniformly over the ground cloth and in the directionof the warp there is one tuft for every six weft or filling yarns,giving a ratio of l to 6 for tufts to picks, and in the direction of theweft, there is one tuft for every two ground warp yarns. If the numberof warp ends per inch is designated by r and the number of filling yarnsper inch is designated by y, the total number of tufts per square inchis then given by however, each tuft l3 furnishes two bundles l4 and [5of filaments which stand substantially straight out from the groundcloth and constitute the pile and the total number of upstanding pilefilament ends is thus given by where a is the number of individualfilaments per tuft. In the various specific construction describedhereinafter, the total number of upstanding pile filament ends persquare inch is calculated from the expression by substituting the valuesfor as, y and 2 given in each example.

The back of the ground cloth also carries a rubber coating I6 or otherbonding agent applied as previously described in an amount not exceeding1 ounce (dried weight) per square yard of fabric. The coating I5 is sothinly distributed that the texture of the warp and filling yarns isclearly visible and apparent to the touch. Nevertheless, the carefullycontrolled application of a bonding agent in this small amount isadequate to provide air and vapour permeabilities within the requiredlimits and firmly to anchor the pile threads in the ground cloth.

Specific examples of pile fabrics constructed in accordance with theinvention are as follows:

Example I =34," NYLON PILE, COTTON GROUND CLOTH kl Bac W rp 2/30 cardedcotton, 48

ends/inch (c). 1/12 carded cotton, 72

picks/inch (y 0.4 1b./square y W, warp thread.

Material nylon; 75 denier monofilament. Filaments/tuft Six (2). Filamentends/m9- 3460 (approx). Fabric weight 2.8 pounds/square yd. Airpermeability 2.0 to 5.0 cu. ft. of air/sq.

{ft/min. (Schiefer & Boynd). Bondmg agent g g ggd g gg :51:

weighing 1 oz./sq. yd.

In the construction of Example I, each tuft consists of six filamentends giving twelve filaments per tuft upstanding from the ground cloth.Applying the parameters of Example I in. the formula N=l-c/d, we have (2equal to 75 and N equal to 3460, giving a is value of 259,500.

Filament ends /in 15,360 (approx.). Fabric weight Air permeability 2.0to 5 .o cu. ftjof air/sq.

ft./m1nute. Bonding agent Rubber, applied to the back oi! the groundcloth and weighing 1 oz./sq. yd.

The construction of Example II affords sixtyfour filament ends per tuftstanding out from the ground cloth. Substituting in the expressionN=lc/d, d is equal to 220/16, and 7c is then equal Example III 10 NYLONPILE COTTON GROUND CLOTH Backing:

Warp 2/30 carded cotton, 62

. ends/inch.

Filling 1/40 carded cotton, 92

picks/inch. Weight 0.24 lb./sq. yd. 15 Pile:

Length inch.

Weave W, warp thread.

Material Nylon; 220 denier, 16 filament used singly.

F laments/tuft Sixteen.

Filament ends/1113..---- 15,400 (approx.).

20 Fabric weight 15.4 ozs./sq. yd.

All permeability 2.0 to 5.0 cu. ft. of air/sq.

ft./minute.

Bonding agent Rubber, applied to the back of the ground cloth andweighing 1 oz./sq. yd.

r In the construction of Example I11, k is equal Example IV NYLONPILENYLON AND COTTON GROUND I CLOTH Backing:

Warp 140 denier, 68 filament nylon, 64 ends/inch. Filling 1/40kc/airde1dcotton, 104

pic s he Wei ht Pile: g 0 24 lb./sq. yd.

Length inch.

Weave W, warp thread.

Material Nylon;t 220 denier, l6 fila- Filaments/tuft siz t gn smglyFilament ends/in. 17,700 (approx).

Fabric welght 17.1 ozs./sq. yd.

Air permeability 1.0ftt(/) 4.0 cu. ft. of air/sq.

. minute.

40 Bonding agent Rubber, applied to the back of the ground cloth andweighing 1 oz./sq. yd.

In the construction of Example IV, is is equal to 243,375. Theconductivity factor of the material of Example IV has been measured andfound to be 0.58 B. t. u./hour/per sq. ft./inch th1ckness.

Example V cg" NYLON PILE, NYLON GROUND CLOTH 54) Hacking:

Warp 140 denier, 68 filament nylon, 62 ends/inch. 25

F n turns/ 1nch.

ng l75 den1er spun nylon, 103

W l ht picks/inch.

Pile: e g 4.8 ozs. per square yard.

warp thread. Material Nylon; 215 denier 17 filagilgnn enitzs/tuift/u seeii t ee r f singly. 1 en ensin 17,700 a 1r lpermeability 0.4 cu. ft. ofair/sq. ft. /min.

on mg agent Rubber, synthetic, applied to go b21031: of thehground 0 anwe o l/sq' yd 1,, mg 1 The pile fabric may be treated, for example.

55 after weavmg and before or after bonding, de-

p ndmg upon the bonding agent employed, by

a chem1cal surface agent to give the fabric a high degree of waterrepellency and a low water absorptlon. The silicones, such as aminosilane or the methyl chloro silanes, having a high contact angle withwater have been found to serve as suitable surface agents. The aminosilanes may be applied from solution or in the form of the llqllld perse and the methyl chloro silanes may be applied from emulsion. Thus, thewoven absentee l-l pile fabricmay be immersed in a 1% solution ofaminosilanein carbon; tetrachloride and then passed'throug-hwringer-rolls under pressures of the o rder of 200*lbs. per inch'widthof fabric and afterwards through a curing oven at 350 F.

over the weft yarns of the backing. The pile-file.

ments are therebyindividually exposed to thebonding agent sofacilitating their firm anchorage in the ground cloth and the bondingagent is extended so that the required air and vapour for four minutes.The weight of silicone applied 5 permeabilities can be secured withaminimum" is about oz./sq. yd'ona; pile fabric. The weightof bondingmaterial. chemical surface agent may alternatively be ap- The vapourpermeabilities of representative 7 plied to the yarn before weaving.samples of caribou skin andof our improved'pile Thecalculated overallbulkdensitiesof pile 10 fabrics have been measured in terms of theirfabrics constructed inaccordance with Examples water-vapourtransmission; rates at various tem- I to V' are as follQWS. I: peraturedifierentials and the results are set -fi f io 'th i h tab .zan 3 belExample I ?45'. i1e. 75 'denier filaments) 5.0 n t e 16S d Example II lj f pile, -13i7- denier filaments) 7.... 2.7 TABLE 2 %xample 7 pille,genier filaments)" 2.4 15

xamp e pi eenier amen s Egample v pile; 121i denier filamentsguunf L1Combou slams as used in clotrmzg The bulk; densitiesset forth above werecalcu- Temperature and H O Temper'a'tme' ail 1 i Z lajted 1.3mm wmgbfi bY vapour pressure flll vapour pressure on g ggg y zgzg glven 1n ExamplesI to. V. by. mult1 p ly1ng the. back p e de weight per square footoffabric by the number 0f. the; h cknrssesnofl fabricrequired: toefille a.mm, Hg Hg sl footcubewithout- .compressing. It will be appreciat'edthat" the bulk density calculated as 38 29. 9.16 63;.

24 25 13.8 22 above Will be lnversely proportional to tne pile 1&6 1m 23length where the construction of the backing 25 0 37.5 48.5 0 4.6 93 andthe density of .the p le are constant. 3&5 51 0 Thehuk. fllsitypicaribou skin, varies .some- 38 50. -z@ 0.81 55:. what according'tothepeltand the rigour of the TABLE 3.

Nylon pilejabrics Temperature and. Temperatureand; Water H O vapour, HzOvapour vapour Fabric Type pressure on back pressure on pile sidetransmission 0., mm. Hg; C... mgJ1;,- H g gmsjlm/mfl V 28.5 29... 28.59.9 7 Example IIlie pile; rubberized 38 38 9.9 62 v as; 50; -e 3. 0 259Example IV% pile not rubberized. Air

permeability 60.80 cu. ItJmin 38M 50 0 V 4. 6 220 27 27 27 13.5 26Example lv-% pile; rubberized 3B 50: V 0 4.6 194 38,; 50, -19 1.0 202ExampleV-%" pile; rubberized n un 38 50. 160 1.15; 293

dressingtreat-ment' but has a value from about 3.75 toabout 5.3 lbs./cu. ft. The pile fabric in 10 accordance with the; invention thus'has'a'bulk density which-isclosely comparable witlrthebest valuesobtainedjfon caribou, and which is'substantially. constant overanextreme range o filament denier.

The pile Warp yarnsemployed-in. Examples I to V hereof.arepomposedof'aplurality of fi1aments twisted together in some degree to; assist theweaving; process. j The nylon yarn". employed is,. however, such. thatno permanent twist "remains in thepile-yarn after the pile warp threadshave} been cutIfollowing weaving by the known cut pile processesand, asa result, the filaments separate from each other to product a veryregular pile structure with the individual filaments spaced uniformlyvthroughout the pile for a substantial portion of. their vfree'length. Inorder to achieve the necessary pile count in accordance with .theinvention, the pile warp yarns have to be beaten up very tightly in theweft yarns. As a result of this beating up; the individual filaments ofthe weft yarns become-displaced from their twisted cylindrical conditionin the region of the bottoms of the W tufts, and become spread out intoa ribbon formation where they bend It, will be notedrthat theyaporpermeabilities for thenylon pile; fabrics given above all comparefavourablyrwith;those ofacariboil Theall. nylon structure of Egample Vis particularly good in having a high water-vapour transmission rate andan extremely low air permeability (0.4 cu. ft./sq. ft./min.). Thischaracteristic is: highly desirable [and represents a marked improvementover caribou.

Arctic clothing, as exemplified by. Eskimo cloth.- ing, difiers in twomain respects from temperate clothing, namely, in its greater thickness,and in the occurrence of. frost within the. boundaries of theclothing.

he; th ness. s imc--. thine i qu to provide the necessary thermalinsulation but the means byHwhich the necessary thickness is achieveddiffers radically from the measures taken for the same purpose, in.temperate. clothing,v In temperate clothing, the thickness determinesto some extentthe stifinessof the fabric and the individual hasbecomeaccustomed to and tolerant of the restrictions inherent in thedesign and the; materials involved since the forces involved .arerelatively low in" proportion to the energy available-to-the individual.However, in

bending clothing, the bending stress formulae are found generally toapply, so that,

where M b=bending moment,

E=modulus of elasticity,

Z=moment of inertia,

C=radius of curvature to which the neutral axis is flexed.

While the forces at play are relatively inconsequential in temperateclothing, they become appreciable when the thickness of the clothingapproaches the order of two inches, as the magnitude of the moment ofinertia varies as the cube of the distance between the extreme fibres.Although temperate clothing is usually made up of at least two layers,thereby diminishing the forces involved by slip between the layers, slipis most resisted where most required, namely, in the area of the joints,so that the extreme outward fibres may be placed under considerabletension. The mechanical moment so induced is proportional to the tensilestress multiplied by the thickness of the material which becomes anappreciable factor in the utility of temperate clothing.

The design principle employed in temperate clothing is not, therefore,satisfactory for polar region clothing as the restrictive forcesincrease as an appreciable power of the thickness involved. If possible,the forces involved should be relatively independent of the thicknessand should be a minimum value, well within the tolerance levels.

The foregoing criterion is achieved in Eskimo clothing consisting of twocaribou skins worn back-to-back. In this assembly only the two skinsthemselves offer resistance to bending and the distance between theextreme fibres of these skins relative to the overall thickness of theinsulation, is comparatively small. On the outer side of the parkaassembly, the hair offers no resisance to bending as the fibres tendmerely to separate slightly. On the inner parka the hair is compressedto some extent but the force required is relatively small. Furthermore,since the hair of the inner parka faces the wearer, the space betweenthe wearers skin and the skin of the inner parka is filled with softresilient hair which is readily compressed thereby allowing freedom ofmovement to the joints without restriction.

Notwithstanding the desirable properties of caribou clothing, it isdifficult to remove frost from caribou hair without damage to the hide,since caribou guard hair does not possess the requisite tensilestrength. Frost removal is, however, essential since the moisture exudedfrom the body is not all carried away by convection currents next to thewearers skin to escape by Way of various openings; much of this moisturepermeates the inner parka and this moisture eventually passes throughthe inner parka where it reaches turbulent cur-rents of air between theinner and outer parkas. When the wearer retires to a sleeping bag atnight after shedding his clothing, his parka freezes and the frost mustbe beaten out in the morning before it can be at on. Nevertheless, theassembly of caribou skins, back-to-back has, until now, provided bodyclothing of otherwise excellent characteristics,

14 the back-to-back assembly serving to give more than mere freedom ofmovement.

The improved pile fabrics of the invention enable full advantage to betaken of the known Eskimo type of back-to-back assembly without thedisadvantages hitherto attending the use of caribou skins, and enablesother advantages to be gained.

Referring now to the accompanying drawings, as shown in Figure 4, thebody clothing consists of an upper inner parka 2i covering the head,arms and torso and extending to about the crotch. The head coveringconsists of an integral hood 22 provided with a narrow face openingwhich hood is fairly close-fitting, and particularly so around the face.Inner pants 23 cover the body from the waist downwards (as shown indotted lines in Figure 4) and extend approximately to the ankles. Theskirt of the inner parka 2| is worn outside the inner pants 23. Theparka 2i and pants 23 may conveniently be made from a pile fabric as setforth in Exexample III, IV or V hereof and the pile should be turnedtowards the skin of the wearer.

The skirt of the parka 2 l, as well as the ends of the sleeves and theface-opening of the hood 22 are each trimmed with ruffs comprising apile fabric as herein described and having a pile comparable with thatof Wolverine fur or longer. Pile fabric as described in Example II, III,IV or V hereof but having a pile length of about 3 inches mayconveniently be used for the ruffs 24, 25 and 26.

The outer garments of the body clothing are shown in Figure 5 andcomprise an outer parka 2'! covering the head, arms and torso andextending again to about the crotch. As in the inner parka, the headcovering is integral with the parka 2'! and is provided with a narrowface opening trimmed with a ruff 28 consisting, for example, of a pilefabric as set forth in Example I, II, III, IV or V but having a pilelength of the order of 4 inches. Outer pants 29 are also providedextending from the waist downwards terminating slightly below the top ofmukluks 30 so as to provide a short portion which may be tucked insidethe mukluks. The outer parka 21 and pants 29 may conveniently be madefrom a pile fabric as described in Example III, IV or V hereof and thepile should be turned outwards as shown.

The clothing is completed by mitts 3| which may consist of back-to-backlayers of the fabrics of Example III, IV or V or of a single layer ofsuch pile fabric, pile outwards worn over dufile mitts and a footcovering consisting of felt insoles, duffie socks, cluffle Vamps allcovered by the mukluks 30 which consist of a single layer, pile outwardsof the pile fabric of Example III, IV or V joined integrally with aflexible moccasin-dike shoe portion 32 made, for example, of moosehideor other flexible clry-tanned good quality leather giving a good wearingsurface.

The inner and outer garments should be relatively loose-fitting tomaintain an appreciable air space between the inner and outer garments.The inner and outer parkas, therefore, provide elongated bell-shapedinsulation around the body with ventilation from the bottom or skirtcontrolled by the degree of activity of the wearer. Due to thedifference in specific gravity between the warm air next to the body andthe outside air, the warm air remains within the parka system in spiteof the open bottom to the skirts. The back-to-back assembly produces aremark- 15 ably -fiexible body clothing withh-igh".insu1atinfi:qualities and good frostremovaLcharacteristicsz.

No inner and outer boundary.layer: ofxcloth'is necessary in this 1system- (no other: clothing znee'd;

be wornbeneath: the inner garments 1 and anlow'.

Body clothing constructed 'as' described-with ref- 20 erence toFiguresand 5 has, however; been worn by Eskimos in the Arcticand" has been de--clared' by them to beas good astheir traditional caribou clothing.

A- number of field tests-have been -madeinthe Arctic with body-clothinginade from pil'e fabric according to Examples III, IV and v' fon variousperiods under variousconditions of activity; and at exposures 1 down to5'5 and with wind velocities up to- 50 Hi Heme-- sensativeresultsobtainedwith one snbj'ect over= several days' are "set forth" in -Tabl's' 4; 5ancl d below.

In 'these'tests; sk-in--temperatures Were-"meas- 16" supported; on: anelastic; harness;. The. couples terminated azsocketzontthe clothing; andcould; be connected, when required, to a plug joined by leads whichextended-into a warmed room housing the measuring equipment. Under theconditions of the tests, the skin temperature measurements were notaccurate to more than about i1 F. since it was diificult .to keepthermocouples in contact'with the skin and the sub- 'ject had to keepcomparatively still whilezthe measurements: are made whichv inactivityallowed him to cool a little. However, the-figures show the generaltrend of the temperature under the: clothes and: are. lower, nntthigherithamthe 1 true. skin temperatures. It is to be: notedr that certainirofthe; temperatures figuresr are; for? the: thermocouplesinext': to theskinan'd others are; for thermocouples just 1: outsideztherundercloth=mg;

A typicalexperiment was: as follows: The subject dressedafter-aHhisclothing had been weighed; first putting on the: thermocoupleharnessxeith'er nextto his skin-or over his under clothes.. When completely:dressed his totalweightwasmeasuredi He then performed. some task; suchas dragging a loaded sled from' a' know-11'distance;- At the .end: ofthis work his skin temperatures were measured": and he: 1 was re.-weighed and hisobservations concerning the clothing were recorded. Bythese meanspdatawere collectedi. regarding the. Warmth of." theclothingmnder various conditions (Table .4), the changes in. weight.fr'omcday to day (Tables' 5A and 5H) and the overall 'change tin:weight' dur ured byway ofcopper-constantan thermocouples 35 ns-theteStsXTablezd):

TABLE 4 Subject: :A.',

Clothing:

Balaclava, woolen;-

Inner'and outer'parkas -Eskimo sty1e;;%'fnylon.plle (Example'V). Innerand outer pants, Eskimo style, nylon pile (E'xampleLV). Flannelettepyjama tops. Army braces:-

Felt'insoles. Dufiie socks; Thermocouple harness.

Dfuflfia vamps;. Canvas mukluks, with moosehide soles Dufiie mitts.Nylon pile'mitts-..

Date andWeather. Activity.-

Temperatures in clothing (F.) Comfort during Test 10 -,Feb. Clear withgood visibility.

29 F. Wind-SE 16mph.

Light exercise walking down and into wind 'over snow-covered ice. onlake.

Medium work. Shovelling 11 Feb. 26 F. Light Wind. Clear and sunny.hard-packed snow=- for 2% homer:

12 Feb. 12 F. Wind 8'. 16 mph. Hard Iwork. Pulling heavily Clear. loadedsled. overlevel but;

. rough.icaandsnow-suriace.

l5 Feb.. l8 F. Wind N. 29mph; Cross. country walk over hilly Clear skycountry for 2 hrs;

16 Feb. 19'F; Wind N. 26 mph. Light exercise. Walking on alr- Olearsky;Driving'snow. strip...

Working'at clearing snow around Driving snovw igloo? Walk overhilly.country to visit traplines; approx. 4 hours walk..-

19 Feb. 42 F; Wind N. Light.

Bright and clear.

Pulled. sledge loaded to 80 lbs. over rough snow for 5 miles. {fried tokeep ,bolow sweating eve 20 Feb. 3l F. Wind light.

and clean Bright (Thermocouples outsidepy Comfortable in general, butback tops) cook. Handsr'ani feet warm; Fingertips cool.- Face cold whenwalking intowind'.-

Comfortable; No dranghts' any where-.2. Handsand feet; warm;

Wa'rrn-and sweating while working.

No draughts' except when standing waiting for T. 0.. measure-v mcnts.Hands sweating."

' Warm at alltimes. Hands and thermocouple measure. feet warm.Froze'tipof nose.

ments.

(Thermocouple harness over' Comfortable in first part of exercise. pyama tops) Cool on second part. Frozeiside Back of neck 81 of nose.Left-armpit... 89 Y Comfortable'gene-rally. Face-cold.

- Eyelashesiroze together at times. Feet Warm. Hands warm except thumbwhere pile is compressed by shovel handle.

Comfortable walking; Hands and feet warm. Nose r0ze.5 times during thewalk. Bodycooled rapidly wvhen standing still at traps.

Very comfortable. Feet warm but some because of. ill-fitting insoles.Hands too warm. Hoar frost appeared on pile.

ouple arne to skin) (Thermoc TABLE A Changes in weights of clothingduring test SUBJECT: A

Date lOFeb. l1Feb.12Feb 15Feb. 16 Feb. 5

Garments Wei his in grams):

Inner nd inter parkas 3, 000 3, 000 2, 950 2,950 3, 075 Inner and outerpants. 1, 920 l, 930 1, 910 1,910 1, 960 l yjalma tops 285 290 280 s.-use 6 610 610 600 696 605 380 400 420 460 495 300 335 s30 Athletic suport... 77 77 Balaclava 108 118 120 Mandand )Garments (in lbs.

an ozs.

Before test 183/3 182/5 182/7 180/11 After test 183/3 182/5 181/1 TABLE53 Changes in weights of clothing during test SUBJECT: A (Continued)Date 17 Feb. 19 Feb. 20 Feb.

Garments Wei hits in grams):

Inner a nd o uter parkas 3,100 3,150. 3,100 Inner and outer pants 1, 9701.965 1,955 Pajama tops 290 Insoles Woolen gloves. Man and Garments:

Before test l.

179/12"... After test TABLE 6 [Clothes were worn from February 8 to 21.They were then dofled and weighed. Later they were room dried andreweighed.]

SUBJECT: A

Weights in grams Articles Damp Dry Inner parka 1, 515 1, 440 Outer parka1, 575 1, 475 Inner pants 880 865 Outer pants 975 950 Insoles 80 Dufliesock li it nm E Mukiuks 435 325 Duflle and Pile mitts 340 265 The lowair-permeability of the fabrics in accordance with the invention leadsto outstanding uniformity of temperature within the suiting; this factwas strikingly demonstrated during early field tests by one subject whowore a suit of fabric according to Example IV but in which the rubberbonding agent was inadvertently insuflicient so giving rise to a highlypermeable fabric. This observer was forced to take shelter after 15minutes exposure; on the other hand a similar suit with fabric of therequired air permeability was very warm while walking at a wind chill of2300 kg. cals./sq. m./hour, expressed in terms of the Wind Chill Tablesappearing for example in Measurements of Dry Atmospheric Cooling inSub-Freezing Temperatures by Siple and Passel, Proceedings of AmericanPhilosophical Society, vol. 89, No. 1, 1945.

From our tests we conclude that the pile fabric of the invention madeinto Eskimo type clothing 18 is adequate for survival under the worstconditions encountered. Under somewhat milder conditions, the wearerwould be able to work in relative comfort even though the total weightof the clothing is only about 14 lbs.

Moisture accumulation in the clothing worn for long periods is notconsidered to be serious. The high water vapour permeability of thefabric was clearly shown by the collection of hoarfrost on the outerpile hairs when the wearer was working hard, pointing to the fact that aconsiderable amount of water vapour had passed completely through thefabric layers.

It is necessary, of course, to give the clothing more care than iscustomary in normal, temperate region, life. Thus, snow and frost shouldalways be beaten out of the garments and ice should be removed from theparka ruff after wear. If this is done, and the outer garment hung up todry, quite considerable drying can occur even in the conditions inside asnow-house with a maximum air temperature of around +25 F.

The field tests have proved satisfactory in all respects and demonstratethat polar clothing constructed as described above of pile fabric ofExamples III, IV and V with pile lengths ranging from A. to inchesprovides the required thermal protection to the wearer with minimum bulkand stiffness and combines the best features of caribou with those ofWolverine and results in clothing which is superior in performance toany cold weather suiting yet devised. A saving in weight of ten poundshas been achieved over nonnative clothing of limited comparableperformance with a remarkable improvement in flexibility.

What we claim as our invention is:

1. A lightweight flexible pile fabric for cold weather clothingcomprising, a flexible ground cloth of interlaced yarns and a pilesurface having substantially smooth-surfaced artificial filamentsanchored in interlaced relationship thereto, said filaments having adenier per filament within the range of about 10 to and being flexibleat and retaining their strength at the sub-zero temperatures obtainingunder polar conditions, and having a tensile strength per filamentgreater than about 1.36 gms. per denier and exhibiting low moistureabsorption at high relative humidities, said pile fabric having astructure modified from the original to provide pores to give to thefabric a low air transmission rate less than substantially 10 cubic feetper square foot per minute at A inch water pressure differential.

2. A lightweight flexible pile fabric for cold weather clothingcomprising, a flexible woven ground cloth and a pile surface havingsubstantially smooth-surfaced artificial filaments anchored thereto ininterlaced relationship, said filaments having a denier per filamentwithin the range of about 10 to 75 and being flexible at and retainingtheir strength at the sub-zero temperatures obtaining under polarconditions, and havin a tensile strength per filament greater than about1.36 gms. per denier and exhibiting low moisture absorption at highrelative humidities, the filaments of said pile surface having a minimumfree length of approximately A; inch, said fabric having a structuremodified from the original to provide pores to give to the fabric a. lowair transmission rate less than substantially 10 cubic feet per squarefoot per minute at inch water pressure differential.

';A l htweight flexible pile fabric for cold weather clothing comprisina flexible Woven ground cloth and a pile surface having substam tiallysmooth-surfaced artificial filaments anchored thereto, said filamentshaving a denier per filament within the range of about 10 to 75 andbeing flexible at andretaining their strength at the sub-zerotemperatures obtaining under polar conditions, and having a tensilestrength per filament greater than about: 1.36- g-ms. per denier andexhibiting low moisture absorption at high relative humidities, thefilaments of said pile surface having a minimum free length ofapproximately inch, said fabric having a structure modified from theoriginal to provide pores to give the fabric a low air transmission rateless than substantially 10 cubic feet per square foot per minute at inchwater pressure differential,,said fabric having a low overall bulkdensity calculated at less than about 5.0 lbs. per cubic foot.

4. A lightweight flexible pile fabric for cold weather closingcomprising, a flexible woven ground cloth and a pile surface havingsubstantially smooth-surfaced artificial filaments anchored in wovenrelationship thereto, said filaments having a denier per filament withinthe range of about 10 to 75 and being flexible at and retaining theirstrength at the sub-zero temperatures obtaining under polar conditions,and having a tensile strength per filament greater than about 1.36 gms.per denier and exhibiting low moisture absorption at high relativehumidities, the filaments of said pile surface having a minimum freelength of approximately inch,

said fabric having a structure modified from the original to providepores to give to the fabric a low air transmission rate less thansubstantially 10 cubic feet per square foot per minute at inch waterpressure differential and, a high water vapor transmission rate greaterthan approximately 20 gms. per square meter per hour at 10 mms. watervapor pressure differential measured at body. temperatures at one sideand at 0 C. on

the other side of the fabric, said fabric having a low overall bulkdensity calculated at less than about 5.0 lbs. per cubic foot.

5. A. lightweight flexible pile fabric for cold weather clothingcomprising, a flexible woven ground cloth and a pile havingsubstantially smooth-surfaced straight artificial filaments anchored inwoven relationship thereto, said filaments having a denier per filamentwithin the range of about 10 to '75 and being flexible at and retaining.their strengthat the sub-zero temperatures obtaining under polarconditions, and having a tensile strength per filament greater thanabout 1.36 gms, per denier and exhibiting low moisture absorption athigh relative humidities, the filaments of said pile having a minimumfree length of approximately inch, said pile having a number of suchfilament ends per square inch given by the quotient of the expressionk/d where is has a value between 200,000 and 300,000 and where d is thedenier of the filaments, said fabric having a structure modified fromthe original'to provide pores to give to the fabric a low airtransmission rate less than substantially 10 cubic feet per square footper minute at inch water pressure differential.

6. A lightweight flexible pile fabric for cold weather clothingcomprising, a flexible woven ground cloth and a pile havingsubstantially smooth-surfaced straight nylon filaments anchored in wovenrelationship thereto, said filaments having a denier per filament withinthe range of about 10. to 75, the; filaments of said pile surface havinga minimum free length of approximately inch, said pile having a numberof such filament ends per square inch given by the quotient of theexpression k/d Where It has a value between 200,000 and 300,000 andWhere d is the, denier of the filaments, said fabric having pores togive to the fabric a low air transmission rate less than substantially10 cubic feet per square foot per minute at inch water pressuredifferenti l.

'2. A lightweight flexible pile fabric for cold weather clothingcomprising, a flexible ground cloth and a pile surface havingsubstantially smooth-surfaced artificial filaments anchored thereto,said filaments having a denier per -filament within the range, of about10 to 75 and being flexible at and retaining their strength at thesub-zero temperatures obtaining under polar conditions, and having atensile. ngth p r filament greater than about 1.3.6, grns. per denierand exhibiting low moisture absorption at high relative humidities, thefilaments of said pile surface having a minimum free length ofapproximately inch, said fabric having a structure modified from theoriginal to provide. pores to give to the fabric a low air transmissionrate less than substantially 10 cubic feet per square foot per minute atinch water pressure differential, the pile surface of said fabricconsisting of filaments selected from the group comprising, thepolymeric amides known generally as nylon, vinyl resins, vinylideneschloride polymers and polyacrylonitrile.

8. A lightweight flexible pile fabric for cold weather clothingcomprising, a flexible ground cloth and a pile surface havingsubstantially smooth-surfaced artificial filaments having a denier perfilament Within the range of about 10 to '75 and being flexible at andretaining their strength at the sub-zero temperatures obtaining underpolar conditions, and having a tensile strength per filament greaterthan about 1.36

;' gms. per denier and exhibiting low moisture absorption at highrelative humidities, the filaments of said pile having a minimum freelength of approximately inch, the pilefilaments being anchored to theground cloth by a bonding agent, the finished fabric having poresproviding a low air transmission rate less than substantially 1c cubi fe p q ar f ot per minute at a /9, inch Water pressuredifferential.

9. A lightweight flexible pile fabric for cold weather clothingcomprising, a flexible ground cloth and a pile surface havingsubstantially smooth-surfaced artificial filaments having a denier perfilament within the range of about 3.0 to 75 and being flexible at andretainin their strength atv the sub-zero temperatures ob.- taining underpolar conditions, and having a tensile strength per filament greaterthan about 1.36 gms. per denier and exhibiting lowmoisture absorption athigh relative humidities, the filaments of said pile having a minimumfree length of approximately inch, the pile filaments being anchored tothe groundcloth by a bonding agent, th finished fabric having poresproviding a low air transmission rate less than substantially 10 cubicfeet per square foot per minute at a inch water pressure differential,and a minimum water vapor transmission per square meter per hour of 20ems at a vapor pressure differential of 10 mm, of mercury meas- 21 uredat body temperatures at one side and C. on the other side of the fabric.

10. A lightweight flexible pile fabric for cold weather clothingcomprising, a flexible ground cloth of woven nylon filament yarn and apile having substantially smooth-surfaced straight nylon filamentsanchored in woven relationship to said ground cloth, said filaments ofsaid pile having a denier per filament within the range of about to 75and having a minimum free length of approximately A inch, said pilehaving a number of such filament ends per square inch given by thequotient of the expression lc/d where k is the value between 200,000 and300,000 and where d is the denier of the filaments, the ground clothhaving a rubber bonding agent deposited on the back thereof, the bondingagent being present in an amount not exceeding approximately one ouncedried weight per square yard of fabric, the finished fabric with poresproviding a low air transmission rate less than substantially 10 cubicfeet per square foot per minute at inch water pressure differential, anda minimum water vapor transmission per square meter per hour of gms. ata vapor pressure differential of 10 mm. of mercury measured at bodytemperatures at one side and 0 C. on the other side of the fabric, saidfabric having a low overall bulk density calculated at less than about5.0 lbs. per cubic foot.

11. A lightweight flexible pile fabric for cold weather clothingcomprising, a flexible ground cloth of woven textile fabric and a pilehaving substantially smooth-surfaced straight nylon filaments anchoredin woven relationship thereto, said filaments having a denier perfilament within the range of about 10 to 75 and having a free lengthranging approximately from A; inch to inch, said pile having a number ofsuch filament ends per square inch given by the quotient of theexpression k/d where It has a value between 200,000 and 300,000 andwhere d is the denier of the filaments, the finished fabric having astructure modified from the original to provide pores to give to thefabric a low air transmission rate less than substantially 10 cubic feetper square foot per minute at a inch water pressure differential.

12. A lightweight flexible pile fabric for cold weather clothingcomprising. a flexible ground cloth of woven textile fabric, and a pilesurface having substantially smooth-surfaced straight nylon filamentsanchored thereto in woven relationship, said filaments having a denierper filament Within the range of about 10 to and having a free length ofapproximately 1%; inches, said pile filaments being anchored to theground cloth by a rubber bonding agent deposited over the back of theground cloth to bond the pile filaments to the woven textile fabric ofthe ground cloth, the fabric thus modified having a structure with poresto give to the fabric a low transmission rate less than substantially 10cubic feet per square foot per minute at inch water pressurediiferential.

WILBUR ELLIOTT COWIE. ARTHUR EUGENE BLOUIN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,896,183 Manson Feb. 7, 1933 2,070,335 Hiers Feb. 9, 19372,238,098 Bradshaw Apr. 15, 1941 2,386,259 Norton Oct. 9, 1945 2,397,808Riding Apr. 2, 1946 2,439,689 Hyde Apr. 13, 1948 2,502,286 Sowa Mar. 28,1950 FOREIGN PATENTS Number Country Date 118,839 Australia Aug. 17, 1944

